It is planned to carry out an extensive investigation of several areas of statistical methodology for the design and analysis of experimental studies, planned or observational, applicable to various areas of health research including cancer, toxicology, environmental health and epidemiology. The objective is to provide more efficient statistical methods to achieve valid conclusions at less cost in terms of time and sample size. Among the problem areas to be considered are sequential methods for clinical trials (including early stopping, interim analyses and "repeated confidence intervals"), statistical design and analysis of animal survival/sacrifice experiments, and general statistical problems related to the analysis of survival data.